JP3199815B2 - Densitometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a densitometer for measuring the concentration of suspended substances, for example, the concentration of sludge, pulp and other various dissolved substances in a liquid. About the total.

[0002]

2. Description of the Related Art Conventionally, when measuring the concentration of a fluid to be measured, an ultrasonic densitometer as shown in FIG. 4 has been used. In this densitometer, a detection pipe 3 is mounted between pipes 1 and 1 'extending on both sides via gate valves 2 and 2', and furthermore, the pipe wall of the detection pipe 3 comes into contact with the fluid to be measured. The ultrasonic transmitter 4 and the ultrasonic receiver 5 are respectively arranged to face each other, and the ultrasonic oscillator 6 is connected to the ultrasonic transmitter 4 side, and the ultrasonic attenuation rate measuring circuit 7 is connected to the ultrasonic receiver 5 side.
Is connected.

According to the densitometer having such a configuration, when an ultrasonic signal is input from the ultrasonic oscillator 6 to the ultrasonic transmitter 4, the ultrasonic transmitter 4 emits ultrasonic waves. This ultrasonic wave propagates through the fluid in the detection pipe 3 and is received by the ultrasonic receiver 5. At this time, the intensity of the ultrasonic wave attenuates according to the concentration of the suspended substance in the fluid. The ultrasonic receiver 5 converts the electric signal into an electric signal corresponding to the reception intensity of the ultrasonic wave and introduces the electric signal into the ultrasonic attenuation rate measuring circuit 7. In the ultrasonic attenuation rate measuring circuit 7, since a calibration curve indicating the relationship between the concentration of the suspended substance and the attenuation rate of the ultrasonic wave according to the concentration of the suspended substance is set in advance, the input electric signal The concentration can be measured from the calibration curve based on the attenuation rate obtained from the above.

[0004]

However, the above-described densitometer has the following problems.

[0005] b. Since the ultrasonic transmitters and receivers 4 and 5 are in contact with the liquid, suspended matter adheres to the contact surface and causes a measurement error. Therefore, it is necessary to periodically clean the liquid. Particularly, in the case of a suspended substance such as sewage sludge, it is liable to adhere to the suspended substance, so that it is necessary to frequently wash the substance.

[0006] b. On the other hand, the above problems are
The problem can be solved by attaching the ultrasonic transceivers 4 and 5 to the outside of the detection pipe 3, but in this case, the thickness of the transmission / reception apparatus mounting portion of the detection pipe 3 must be reduced.
There is a problem in terms of strength and durability. In addition, piping 3
And is susceptible to vibrations, which can cause errors.

C. Ultrasonic waves have a much higher attenuation rate in gas than liquid. This means that when bubbles are mixed in the fluid, the attenuation of the ultrasonic waves in the gas is much larger than that of the suspended matter. As a result, the measurement becomes impossible or the measurement is performed at a higher concentration than the apparent.

Therefore, a defoaming type densitometer is used in this type of densitometer. This defoaming type densitometer is configured to take a fluid to be measured into a pressurized defoaming chamber at a predetermined sampling cycle, dissolve bubbles by pressurization, and measure the concentration of the fluid to be measured. However, in this densitometer, the fluid is sampled at a predetermined sampling cycle, so that continuous measurement cannot be performed. Further, since sampling and pressurization are performed, a mechanical movable mechanism needs to be provided, and thus the reliability is low.

D. Further, such a densitometer utilizes the fact that ultrasonic waves are dispersed and attenuated by the substance to be measured, and thus is difficult to apply when the suspended substance is completely dissolved in the fluid.

The present invention has been made in view of the above circumstances, and can measure the concentration of a substance to be measured without being affected by the adhesion of a suspended substance or bubbles in a fluid. An object of the present invention is to provide a densitometer that can reliably measure even when dissolved in water and that efficiently transmits and receives microwaves when using a microwave transmitting and receiving method.

[0011]

According to a first aspect of the present invention, in order to solve the above-mentioned problems, a microwave transmitting / receiving antenna is disposed to face a detecting tube (including a detecting container), phase delay obtained by propagating the microwave circuit as a reference becomes fluid or reference in the detection pipe body θ
By using the _A, and a phase delay theta _B obtained by propagating the microwave in the fluid to be measured containing the substance to be measured in the detection tube body, the phase difference Δθ = θ _B -θ _A

A concentration meter for measuring the concentration of the fluid to be measured from the phase difference Δθ after calculating the phase difference Δθ by the following arithmetic expression, wherein the densities are opposed to each other across the center axis of the detection tube. forming an opening window in the tube or container, and the antenna mounting insulators attached hermetically against further antenna mounting insulators to those open window portion, the antenna
The microwave transmission / reception, wherein the opening is filled with a dielectric material
Those mounted in close contact with the system antenna.

Next, a second aspect of the present invention is to fill the antenna opening with a dielectric such as ceramics.
This makes it possible to reduce the size of the antenna and facilitate impedance matching. Further, by processing the surface of the dielectric in accordance with the shape of the microwave transmitting / receiving antenna mounting portion of the detecting tube, the adhesion can be improved, and the leakage of radio waves can be reduced as much as possible. That is, it can be attached to, for example, a bend.

According to a third aspect of the present invention, the antenna mounting insulator is made of the same material as the dielectric material filled in the opening of the antenna or a material having a similar dielectric constant and magnetic permeability. It is configured using the above.

[0015]

Therefore, the inventions corresponding to the first and second aspects of the present invention take the above-described measures to make the microwave propagate in the fluid containing no substance to be measured and in the fluid containing the substance to be measured. And measure the phase delays θ _A and θ _B respectively.
After calculating the phase difference △ θ from these phase delays θ _A and θ _B ,
Since the concentration of the fluid to be measured is measured using a calibration curve that represents the relationship between the predetermined known concentration and the phase difference, even if the fluid contains bubbles, the microwave propagates without being affected by the bubbles. The concentration of the substance to be measured can be measured as well, and even when the suspended substance is dissolved in the fluid, the microwave propagates and reaches the receiving system while being affected by the dissolved substance. The concentration can be measured.

Further, an antenna for a microwave transmission / reception system is closely attached to an opening window at a position opposed to the tube axis of the detection tube with an antenna attachment insulator interposed therebetween. For the insulator for the antenna, use the same material as the material of the dielectric filled in the opening of the antenna, or a material with a similar value of the dielectric constant and the magnetic permeability of this member, so that the contact boundary of the insulator The reflection of the microwave on the surface can be reduced, and the microwave can be efficiently incident and emitted.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The principle of measuring the concentration of a densitometer according to the present invention will be described below with reference to FIG. Generally, microwaves have a problem because they propagate on the outside of the tube without passing through the tube wall when using a metal tube. Also, even when using an insulated tube or container, the microwave depends on the mounting state of the antenna. Wave reflection is a problem. Therefore, the concentration meter of the present invention is to measure the concentration of the fluid to be measured by using the phase delay of the microwave reception wave while solving such a problem.

That is, this densitometer is provided with a microwave transmitting antenna 12 on both sides of a metal tube (hereinafter referred to as an insulating tube) 11 on which an insulating tube, a container or a partly insulating material is attached. The receiving antenna 13 is placed in opposition with the antenna in close contact, and microwaves are transmitted from the transmitting antenna 11 side.

At this time, when the zero water 14 is contained in the insulating tube 11 as shown in FIG. 1A, the microwave propagates through the fluid of the zero water 14 through the insulating tube wall. is received at the opposite side of the receiving antenna 13 while, but the phase delay of the microwave receive wave at this time is theta _a.

On the other hand, as shown in FIG. 2B, when the fluid to be measured containing the substance to be measured is contained in the insulating tube 11, the microwave is transmitted from the transmitting antenna 12 and the insulating tube wall is also formed. a phase delay theta _B upon reception by the receiving antenna 13 on the opposite side while propagating the measurement fluid containing a substance to be measured through. Incidentally, both of these phase delays θ _A and θ _B can be obtained from the following theoretical formulas.

[0021]

(Equation 1) Where c ₀ : velocity of radio wave propagation in vacuum d: thickness (distance) of the fluid layer to be measured ω: angular frequency of incident microwave ε ₀ : dielectric constant of vacuum ε _W : relative dielectric constant of zero water ε _S : relative dielectric constant of the fluid to be measured σ _W : electrical conductivity of zero water σ: electrical conductivity of the fluid to be measured Then, the phase difference か ら θ from these two phase delays θ _A and θ _B
Is

[0022]

(Equation 2)

## EQU2 ## Therefore, when measuring the concentration of the fluid to be measured including the substance to be measured, the above-described FIG.
The phase delays θ _A and θ _B are measured based on the measurement principle of (b), and the phase difference Δθ = θ _B −θ _A is calculated based on the equation (3). If a calibration curve indicating the relationship with the phase difference is used, the concentration of the fluid to be measured can be measured from the measured phase difference Δθ.

Next, one embodiment of a densitometer according to the present invention will be described with reference to FIGS. Note that FIG.
FIG. 3 is an overall configuration diagram of the densitometer, and FIG. In these drawings, reference numerals 21 and 21 'denote an upstream pipe and a downstream pipe, respectively.
Concentration detecting tubes 23 are interposed between 1 'via gate valves 22, 22', respectively. The concentration detecting pipe 23 is provided with a water supply valve 24 and a drainage valve 25, so that zero water can be introduced from the outside.

As shown in FIG. 3, the concentration detecting tube 23 has opening windows 23a and 23a 'for microwave input and output, respectively, at positions opposed to each other with the tube axis interposed therebetween. The antenna mounting plates 23c and 23c 'are attached to the opening windows 23a and 23a' via airtight seal packings 23b and 23b '. As shown, the antenna mounting plates 23c and 23c 'are fitted with insulators 23d and 23d' so as to maintain airtightness only in portions corresponding to the incidence and emission of microwaves, or the whole is made of an insulator. Used.

These antenna mounting plates 23c, 23
A transmitting antenna 28 and a receiving antenna 29 are individually attached in close contact with c '. The openings 28 'and 29' of the antennas 28 and 29 are filled with dielectrics 30 and 30 'such as ceramics.

On the other hand, the antenna mounting plates 23c, 23
The antennas 28 and 29 are in close contact with c ', but when transmitting microwaves from the transmitting antenna 28 and when the insulator 23d'
When the microwave passing through the antenna is received by the receiving antenna 29, the antennas 28 and 29 and the insulators 23d and 23d 'are received.
A part of the microwave propagating at the interface with the surface is reflected. Therefore, in order to reduce the reflection of microwaves at the contact boundary surface, the insulators 23d and 23d 'are filled with the dielectrics 30 and 3 filled in the openings of the antennas 28 and 29.
It is assumed that the same material as the material of 0 'or a material having a similar value of dielectric constant and magnetic permeability is used. The reason is that the reflection coefficient of microwave is

[0028]

(Equation 3)

This is because they are proportional to each other as described above. Here, ε _S1 and μ _S1 are the antennas 28 and 29, respectively.
Ε _S2 and μ _S2 are the relative dielectric constants of the insulators 23d and 23d ', respectively.
It is relative permeability. Normally, μ _S1 and μ _S2 are almost 1, so that the relative permeability ε _S2 of the insulators 23d and 23d 'is smaller when the value is as close to ε _S1 as possible, and furthermore, ε _S2 = ε _S1
And the antennas 28, 2 are attached to the insulators 23d, 23d '.
If 9 can be adhered, the reflection can be made almost zero.

Next, returning to FIG. 2, the configuration of the densitometer will be described. The transmission system of this densitometer is provided with a microwave oscillator 31 for generating microwaves.
The output of 1 is sent to the transmitting antenna 28 via the power splitter 32. On the other hand, in the receiving system, the receiving antenna 2
9 is provided with a phase measuring device 33, which is supplied with not only the microwave receiving wave from the receiving antenna 29 but also a part of the microwave transmitting wave from the power splitter 32 as a reference signal for comparison. ing.

The phase measuring device 33 has the configuration shown in FIG.
_A phase delay measuring means 33a for measuring the phase delays θ _A and θ _B under the measurement condition (b), a measurement data storage means 33b for storing the phase delay data, and a phase difference calculating means 33c for obtaining the phase difference Δθ are provided. Have been. Reference numeral 34 denotes a signal converter which receives a signal corresponding to a phase difference from the phase measuring device 33, converts a signal corresponding to the density, for example, a density of 0 to 5% into a current signal of 4 to 20 mA, and outputs the current signal. Next, the density measuring operation of the densitometer configured as described above will be described.

[0032] First, to measure the phase delay theta _A by introducing zero water concentration zero (e.g. tap water) into the density detection tube 23. Here, the phase delay means a delay of the phase of the microwave reception wave with respect to the microwave transmission wave in the phase comparator 33.

In measuring the phase delay θ _A , the gate valve 2
After closing 2, 22 ', the drain valve 25 was opened to discharge the sludge in the tube 23, and then the water supply valve 24 was opened to supply tap water to wash the dirt in the tube 23. rear,
The drain valve 25 is closed to fill the pipe 23 with tap water.

When a microwave signal is generated from the oscillator 31 in such a state, the microwave is transmitted from the transmission antenna 28 through the power splitter 32,
The tap water in the pipe 23 propagates and is received by the receiving antenna 29. The microwave received by the receiving antenna 29 is sent to the phase measuring device 33. This phase measuring device 3
3, a part of the microwave transmission wave is transmitted from the power splitter 32.

Here, the phase delay measuring means 33a of the phase measuring device 33 measures the phase delay θ _A by comparing the microwave transmission wave and the microwave reception wave, and uses the measured phase delay θ _A as its own. It is stored in the measurement data storage unit 33b.

Thereafter, the drain valve 25 is opened to open the pipe 2
After draining the tap water in 3, the gate valves 22 and 22 ′ are opened to flow the fluid to be measured containing the substance to be measured, and the phase delay θ _B is measured. In other words, a microwave is transmitted at a predetermined period or every moment while the fluid to be measured including the substance to be measured is flowing, the phase delay θ _B is measured by the phase measuring device 33 and stored in the measurement data storage means 33b, Stored while updating sequentially as needed.

Further, the phase difference calculating means 33c of the phase measuring device 33 reads out the phase delay θ _B and the already measured phase delay θ _A at the time of supplying zero water from the storage means 33b, and Δθ = θ _B −θ _A

The phase difference Δθ is obtained based on the following arithmetic expression and sent to the signal converter 34. In this signal converter 34,
When the phase difference Δθ is received, the density is determined in advance according to the relationship between the known density and the phase difference, that is, the calibration curve, and is converted into a signal corresponding to the density and output.

In the present densitometer, the opening windows 23 are opposed to each other with the tube axis of the detection tube 23 interposed therebetween.
a, 23a ', and the opening windows 23a, 2a
The antenna mounting plates 23c, 23c 'are hermetically attached to 3a', and the microwave transmitting / receiving antennas 28, 29 are attached to the antenna mounting plates 23c, 23c 'in close contact with each other, and furthermore, insulators 23d, 23d are provided. ', The same material as the material of the dielectric material filled in the openings of the antennas 28 and 29, or a material having a similar value of permittivity and magnetic permeability is used. Can be made substantially zero, and the antennas 28, 2
The reflection of the microwave at the contact boundary between the insulator 9 and the insulators 23d and 23d 'can be reduced, and the incidence and emission of the microwave can be performed efficiently.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the measurement is performed in a state where the sludge is flowing, but the concentration may be measured in a stationary state. Further, the present invention can be applied not only to the measurement of the sludge but also to the measurement of the concentration of another fluid. Further, in the embodiment, the liquid having a concentration of 0% has been described as a reference. However, a liquid which can be regarded as zero concentration in consideration of a measurement range without being strictly zero may be used. Alternatively, a circuit having a certain propagation characteristic may be used as a reference. Further, a container or a bypass tube may be used instead of the detection tube 23, and the concentration may be measured by adopting the configuration shown in FIG. In addition, the present invention can be implemented with various modifications without departing from the scope of the invention.

[0041]

As described above, according to the present invention, since the concentration is measured using microwaves, the concentration of the measured substance can be measured without being affected by the adhesion of the measured substance or bubbles in the fluid. The concentration can be easily measured even when the substance to be measured is completely dissolved in the fluid. In addition, although a method using microwaves is used, a rigid structure can be achieved by using a metallic tube body for the detection, and the antenna can be downsized. It is possible to reduce the reflection and leakage of the microwave at the contact interface with the insulating plate, thereby increasing the microwave input / output efficiency.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of concentration measurement by a densitometer.

FIG. 2 is an overall configuration diagram showing one embodiment of a densitometer.

FIG. 3 is a detailed view of a main part of an antenna mounting portion of the densitometer.

FIG. 4 is a diagram showing a schematic configuration of a conventional densitometer.

[Explanation of symbols]

23 ... Detection tube, 23a, 23a ... Open window, 23
c, 23c ': Antenna mounting plate, 23d, 23d'
... Insulator, 28 ... Microwave transmitting antenna, 29 ... Microwave receiving antenna, 31 ... Microwave oscillator, 32 ...
Power splitter, 33: phase measuring device, 34: signal converter.

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Tsukasa Suzuki 3-26-22 Kasuya, Setagaya-ku, Tokyo (72) Inventor Ikuo Arai 1-48-31, Funabashi 1-chome, Setagaya-ku, Tokyo (72) Inventor Seiji Yamaguchi No. 1, Toshiba-cho, Fuchu-shi, Tokyo Inside the Toshiba Fuchu factory (56) References JP-A-59-19846 (JP, A) JP-A-3-221185 (JP, A) JP-A-63-148834 (JP) , U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 22/00 G01N 9/00-9/36

Claims (3)

(57) [Claims] 1. A microwave transmitting / receiving antenna is disposed to face a detection tube or a detection container, and a microwave is provided in a reference fluid or in a reference circuit in the detection tube or the detection container. position and a second phase delay obtained by propagating the microwave in the fluid to be measured comprising a first phase delay and the measured substance before Symbol detection tube body or detection container obtained by propagating In a densitometer for determining the phase difference and measuring the concentration of the fluid to be measured from the phase difference , an opening window portion is provided in the tube or container so as to face the center of the tube or container for detection. and forming, attached airtightly antenna mounting insulator the opening window portion, relative to the antenna mounting insulator, Ann
The microwave transmission and filling the tener opening with a dielectric.
Densitometer, characterized in that installed closely receiving system antenna. 2. The method according to claim 1 , wherein the dielectric filling the antenna opening is a dielectric.
Induction of ceramics etc. for impedance matching
The densitometer according to claim 1, wherein an electric body is used . 3. The antenna-mounting insulator is made of the same material as the dielectric material filled in the antenna opening, or a material having a similar dielectric constant and magnetic permeability. The densitometer according to claim 1, wherein